Dallas billionaire Harold Simmons is photographed in his North Dallas office.

DALLAS — Dallas billionaire and heavyweight GOP political donor Harold Simmons, who has given tens of millions of dollars to Republican candidates, including Texas Gov. Rick Perry and former presidential candidate Mitt Romney, has died. He was 82.

Simmons, born to two school teachers in East Texas, became one of the richest men in the country with interests ranging from energy to chemicals. Simmons’ spokesman Chuck McDonald said Simmons died Saturday in Dallas. McDonald said he did not know the cause of death.

Perry on Sunday called Simmons “a true Texas giant, rising from humble beginnings and seizing the limitless opportunity for success we so deeply cherish in our great state.”

“His legacy of hard work and giving ... will live for generations,” Perry said in a statement.

Simmons’ wife, Annette Simmons, told The Dallas Morning News her husband died at Baylor University Medical Center at Dallas. She said he’d been in Baylor’s intensive care unit for the last eight days, the newspaper reported. She did not give the cause of death.

Attorney General Greg Abbott noted in a statement that Simmons “shared his success with the state he dearly loved, giving generously to make advancements in healthcare and to improve higher education.”

Simmons’ has given tens of millions to Texas organizations, including charities, medical groups, education groups and civic organizations. Daniel K. Podolsky, president of UT Southwestern Medical Center, said his donations to their institution alone approached $200 million.

He currently sits at No. 40 on Forbes’ list of the 400 wealthiest Americans with a net worth of $10 billion as of the fall, according to Forbes.

“Harold Simmons was one of my best friends, and it’s never easy to say goodbye to close friends,” Texas oil tycoon T. Boone Pickens said in a statement. “Harold accomplished so much in his life. He was a passionate person — passionate about his family, his business, philanthropy and politics. ... We should all leave such a rich legacy behind.”

According to a biography on his namesake foundation’s website, Simmons earned his bachelor’s and master’s degrees from the University of Texas.

He decided at the age of 29 to buy a small Dallas drugstore, according to his biography. He went on to buy Williams Drug Co. in 1966 and 30 more drug stores the next year, followed by an $18 million buyout of Ward’s Drugstores in 1969. He sold his stores in 1973 for $50 million in Eckerd stock. He then started a career as an investor, buying major positions in publicly traded companies.

In 2008, Simmons bankrolled ads linking then-presidential candidate Barack Obama to William Ayers, a Vietnam-era militant who helped found the violent Weather Underground. Simmons was also a key backer of the Swift Boat Veterans’ attacks on Democratic presidential candidate John Kerry in 2004.

Simmons also called Obama “the most dangerous American alive” in an interview with the Wall Street Journal last year.

According to The Dallas Morning News, his foundation has also recently donated $600,000 to Resource Center, a group that serves the city’s lesbian, gay, bisexual and transgender community.

Other donations have included $5 million to the campaign to build the AT&T Performing Arts Center in Dallas.